This conversion is done by Transpec 2.3.4 with the following command:
transpec -c "rake spec" spec/classes/ spec/defines/ spec/spec_helper.rb
* 210 conversions
from: it { should ... }
to: it { is_expected.to ... }
* 19 conversions
from: it { should_not ... }
to: it { is_expected.not_to ... }
* 15 conversions
from: == expected
to: eq(expected)
* 15 conversions
from: obj.should
to: expect(obj).to
For more details: https://github.com/yujinakayama/transpec#supported-conversions